There is conventionally known a linear motion guide unit having a rolling-element chain in which rolling elements are held in a chain to control the behavior of the rolling elements during the rolling motion through the recirculation circuit. The slider is made therein with a guide trough extending along the overall recirculation circuit to fit therein the chain of the rolling-element chain to make sure of smooth travel of the rolling elements throughout the recirculation circuit. Most conventional linear motion guide units of the construction as stated earlier, nevertheless, have needed several more chores to fit snugly the chain into the guide trough cut in the recirculation circuit. Moreover, accurately cutting the guide trough throughout the recirculation circuit in the slider has been proved to be difficult and complex. With the prior linear motion guide units of the construction as stated earlier, the guide trough made in the recirculation circuit eventually leads the slider to sophistication in construction.
A prior rolling-contact guide system is known as disclosed in, for example Japanese Patent Laid-Open No. 66313/1990 in which a carriage is carried for movement relative to a guide rail. Cassettes are secured to both sides of the carriage, one to each side, using fastening bolts to guide a sort of chain composed of a retainer element keeping therein rolling elements including rollers, balls, and so on. The cassettes are composed of shapes of metal sheets, which are fastened to the both sides of the carriage with screws in such a manner that the retainer element fits at the guide shoulder thereof into a guide trough that is formed in the shape of metal sheet. With the rolling-contact guide system constructed as stated just earlier, the retainer element, once assembled into the cassette, is very tough to take it apart out of the cassette.
Another example of the conventional rolling-contact. guide system is disclosed in, for example Japanese Patent Laid-Open No. 68417/1998 in which a carriage is carried for movement along a guide rail through rolling elements including balls, and so on, which fit in a recirculation passage with being kept with an endless retainer. A retainer holder is provided along a side edge of a load raceway groove cut in a carriage body to keep a side of the endless retainer along the load race. The retainer holder is of a resin molding that is made integral with the carriage body high in rigidity. With the rolling-contact guide system constructed as stated earlier, the retainer used to space the rolling elements from each other is installed in a guide trough cut deep throughout the recirculation passage.
With the prior linear motion guide unit disclosed in, for example Japanese Patent Laid-Open No. 89358/1998, a carriage is carried for linear movement along a guide rail through rolling elements or balls, which are kept in place with a chain to make sure of smooth recirculation. The carriage is provided on any side thereof with a fore-and aft raceway groove to make a load race. A ball retainer fits in the side edge of the load race made in the carriage to make engagement with the rolling elements, keeping the rolling elements against coming apart away from one another after the carriage has been disengaged out of the guide rail. The ball retainer is made with a guide construction in the form of a guide trough into which the chain fits on a lengthwise edge thereof for relatively linear movement. For installation of the ball chain into the linear motion guide unit, the carriage is first dismantled of any one of forward and aft end caps to open both the load passage and non-loaded return passage. The carriage is placed upright with facing the open end straight up. The chain is applied to the open end of the non-loaded return passage, followed by being fed into the return passage together with the balls by the use of an intermittent-feed mechanism. After having finished charging the ball chain into the carriage, the end cap is applied to complete the recirculation circuit. Moreover, ball pockets in the chain is so made as to allow the ball making easy engagement with and/or disengagement out of the chain for making certain of smooth assemblage of the ball chain in the carriage.
Disclosed in, for example Japanese Patent Laid-Open No. 54633/2002 is a further another linear motion guide unit, which is comprised of a guide rail having two rows of lengthwise races on widthwise opposite sides thereof, two races to each side, and a carriage carried for linear motion relative to the guide rail by virtue of many rollers, which are held with a roller retainer while allowed to roll through their associated recirculation circuit. A guide member is provided in a way extending along the lengthwise side edges of the load race to form a guide trough to guide the rollers along there. The guide member is composed of first, second and third parts, which are made of resinous material, molded separately from the carriage body. The first part has at forward and aft ends thereof tenons to fit into the end caps, and also has at a lengthwise side thereof elongated openings used to fasten it in place relative to a radially inside guide component. The second part is made at forward and aft ends thereof with tenons to fit into the radially inside guide components. The third part, like the first part stated earlier, has at forward and aft ends thereof tenons to fit into the end caps, and also has at a lengthwise side thereof elongated openings used to fasten it in place relative to a radially inside guide component. On assembling the members, parts, components, and so on stated earlier into the linear motion guide unit, one of the end caps is first mounted to any one lengthwise end of the carriage body and then the first, second and third parts are installed in the carriage body. A retainer band together with the rollers is inserted through the opposing opened end of the carriage body into the recirculation passage. The radially outside and radially inside guide components are attached to the opened end of the carriage body, followed by covered with the associated end cap.
Further disclosed in, for example Japanese Patent Laid-Open No. 130272/2002, which is a co-pending senior patent application, is another example of the linear motion guide unit, in which many separators are sequentially held with a chain in a way spaced away from each other. The slider has a retainer band to keep the rolling elements against coming apart away from one another and also the chain against falling away from the slider after the carriage has been disengaged out of the guide rail. The slider is made with a deep slot to allow the retainer band receding into the deep slot so as to make disengagement with the chain in a phase where the slider is in association with the guide rail.
In Japanese Patent Laid-Open No. 91446/1995, which is a co-pending senior patent application, there is disclosed a linear motion guide unit in which two rows of sequential rollers roll through recirculation circuits in a way intersecting with each other at their turnarounds. A retainer plate is secured to a carriage of a slider by means of a fastening band, which makes engagement with end caps of the slider. With the linear motion guide unit constructed as stated earlier, any adjacent rollers are in direct rolling-contact with one another and the retainer plate has no guide trough.
The prior linear motion guide units stated earlier, nevertheless, pose different issues as will be discussed below.
With the first prior rolling-contact guide system cited above, the carriage is made with subdivisions for the provision of the guide trough where the guide shoulder of the retainer element is allowed to move through there. Thus, the guide system would be less in stiffness. Moreover, since the recirculation circuits are made throughout with using the shapes of metal sheet, the guide system has to be made inevitably on a large scale in the overall construction as well as needs several more chores of finishing the recirculation circuits.
The rolling-contact guide system disclosed in the second citation needs to make integrally retainer holders to provide the recirculation circuits for the ball-retainer combination. The intricate configuration would require sophisticated skill and also complicated work to complete it. Moreover, it would be much troublesome to fit snugly the ball-retainer combination into the guide trough, which has been completed in advance throughout the recirculation circuit.
The third prior linear motion guide unit cited earlier, because the ball retainer is fastened to the carriage body, needs the complex process of combining the balls with the chain prior to introduction of the ball chain into the recirculation circuit in the linear motion guide unit. Moreover, there is the possibility that any ball could unexpectedly fall away out of the chain before charging the ball chain.
With the fourth prior linear motion guide unit cited above, the first, second and third parts must all be set up together relatively to their associated radially inside guide components and end caps to finish the linear motion guide unit. This gets assembling work harder. Moreover, the sophisticated configuration in section of the parts for the guide member may make assembling and production work much troublesome.
Thus, the linear motion guide unit in which the rolling-element chain is assembled into the recirculation circuit in the slider still poses the major challenges about how to make a guide trough with accuracy and ease in the recirculation circuit, how to form the guide trough with using a member simple in shape and how to make the application of the rolling-element chain into the recirculation circuit easier.